Update localized content
Partially updates message content.
Optional content uses exactly one of mjml, html, text, or payload; the API
infers the editor type from that key. Content can only be updated while the parent
campaign is in draft. Non-workflow messages reject duplicate locales with 409 Conflict.
Authorizations
Accepts either a raw API key or Bearer <key>.
Headers
Optional dated API revision for the request. Must use YYYY-MM-DD format.
^\d{4}-\d{2}-\d{2}$"2026-03-01"
Path Parameters
Campaign message ID.
Campaign content record ID.
Body
Localized rows may update locale; the default content variant cannot be localized in place.
Exactly one of mjml, html, text, or payload must be present in write requests.
Email messages accept mjml, html, or text. SMS accepts text. Push accepts payload.
Response
Campaign content updated.
List response item; body copy is omitted — fetch a single record for content.
null for the default content variant.
Full body: exactly one of mjml, html, text, or payload is set.

